Mainsail Furling on a Multihull

A closeup of the gooseneck, showing the mandrel and open boom on an in-boom mainsail furler; note the full-length batten just above the boom. Photos courtesy of Forespar

The defining feature of most modern multihulls is a large, robustly built mainsail, typically with full battens and a dramatic roach. The sails are cut large to maximize the performance for which multihulls are renowned, especially to windward. They are heavily constructed to withstand the loads that result from the boats not heeling before the wind like a monohull.

Unfortunately, this much canvas can make sailing a multihull a real chore, especially for shorthanded crews. Not only does the sheer weight of material make a multihull’s mainsail a bear to hoist, but they can be challenging or even downright scary to reef. Batten cars, luff tracks, lazyjacks, zippered “stack-pack” mainsail covers and slab-reefing systems all go a long way toward minimizing these challenges. But handling the main on a bigger cruising cat, in particular, remains tough, even if it’s just manhandling those last few folds of errant Dacron into its bag at the anchorage. The result is the all-too-many cats you see making their way under power or jib alone, even to windward, on an otherwise perfect sailing day.

Of course, the natural solution to an unruly mainsail is some kind of roller-furling system. However, while mainsail furlers have long been widely accepted aboard monohulls, they are rarely seen on multihulls, which is too bad, given the many benefits they provide.

For years, conventional wisdom has held that roller-furling systems are problematic aboard a multihull, for a number of reasons. In the case of in-mast furling systems, the complaint is that without a full-roach mainsail a multihull’s performance is hopelessly compromised. In the case of in-boom furling, the concern becomes chafe and the reliability of a type of system that has long had a reputation for being fickle.

In both cases, however, conventional wisdom—as is so often the case—while not entirely wrong, is not entirely right either.

The screecher on this Antares 44i helps make up for the lack of roach on the boat’s in-mast furling mainsail. Photo courtesy of Schaefer Marine

In-mast options

Among the most enthusiastic proponents of in-mast furlers aboard multihulls is Jeff Woodman of Antares Yachts, builder of the Antares 44i. According to Woodman, he installed his first Seldén in-mast furler aboard one of his boats at the request of an owner who “wanted one so badly he didn’t care about the price.” Since then, though, he has become a believer himself, estimating that about half of his customers now go with in-mast furling to take advantage of a wide range of benefits, including ease of use, peace of mind and even a better night’s sleep. “It really appeals to those sailors who are nervous about what to do with a fully loaded main as the wind picks up.

Another benefit is that you, your wife or crew can handle it on a night watch without having to wake anybody else up,” Woodman says.

Beyond that, Woodman notes that because of the relatively minor loads involved when rolling in a bit of sail, the crew isn’t dependent on noisy electric winches to fine tune the main: something a fellow shipmate crashed out during their off-watch will appreciate.

As for the loss of sailing efficiency, both Woodman and Seldén’s U.S. manager Scott Alexander say that while in theory you’re going to take a hit, the reality is a bit different. Specifically, while it’s great having a nice, powerful main, all that power isn’t going to do you much good if you’re too intimidated to use it.

And we’re not just talking offshore gales here. How many sailors regularly tuck in a reef much earlier than they would otherwise or just carry a reef as a matter of course while on charter to keep their less experienced crew happy? Even a brief gust from, say, the low teens to 20 knots, can be pretty scary if you don’t know what’s going on, and who needs that kind of stress on a sunny day?

An in-boom furler allows you to use full-length battens and retain a large roach. Photo courtesy of Schaefer Marine

“On passage you will actually get better speeds because you’re using the main more, especially in adverse weather,” Woodman says. “Many criticize the concept by saying you lose too much performance because of the reduction in the roach on the main. [But] just last month, one of our new Antares 44is was sailing north from our Argentine factories and sailed 209 nautical miles in a 24-hour period with our furling main.”

Along these same lines, Alexander notes that with today’s headsail technology, multihull sailors also have a number of other options for adding power to the rig on anything but a beat or close reach, many involving continuous-line furlers specifically designed for cruisers.

Aboard the Antares 44i, for example, a screecher comes standard. Other options include a genoa, A-sail or even a Parasailor symmetrical spinnaker. Similarly, the Discovery 50 catamaran, which is also available with a Seldén in-mast furling system, includes a short sprit for flying various different reaching sails.

That said, there’s no denying that if you go with an in-mast system you will giving up a fair bit performance-wise, especially sailing hard on the wind. So if you plan to do any kind of racing or require a boat that sails well on all points of sail, in-mast furling might not be for you.

In-boom Furling

Despite their performance potential, in-boom furling systems have long been suspect in the eyes of many sailors because of their complexity and reputation for binding. However, as was the case with early headsail furlers, the industry has made great strides in terms of reliability and ease of use, so that they are becoming an increasingly attractive option.

As an added benefit, thanks to their inherent design in-boom furlers offer a kind of “bail out,” as it were, in the event things should ever go haywire. Specifically, because the sail travels up and down a mast track, like a conventional sail, even if the furler fails or jams with the sail up, you can still pull it down and lash it out of the way.

By contrast, because the sail wraps around a mandrel running the length of the luff with an in-mast system, in the event something goes wrong, especially when reducing sail in a blow, things can get complicated fast since you’re stuck with a bunch of sail aloft. Rolling up the sail in the boom also means less weight aloft compared to an in-mast system, in which the entire sail remains fully hoisted when furled.

Of course, the other big advantage to an in-boom furler is that you can continue to use horizontal battens. In fact, full-length battens will help the sail furl that much better. This, in turn, means you can have a sail with plenty of roach. Despite the best efforts of untold sailmakers and hardware manufacturers, there’s just no way you can do this with a mainsail that rolls up vertically. Vertical battens help, but only to a point.

The result is a sail that can be as big and powerful as you like. As Phil Berman, president of the Multihull Company points out, you might not get quite the same performance that you would out of conventional main. But you’re still going to get a sail with an aerodynamic shape that is dramatically superior to one cut so that it can roll up inside the mast.

“In-boom furling is a really neat idea on a catamaran. You can still go with a really roachy main,” says Berman, noting he is currently fitting a Southern Spars in-mast furling unit on hull #1 of his new Balance 526 peformance cruiser and offers Schaefer’s Boom Furling system on the smaller Balance 451.

There’s plenty of room for a vang with this in-boom furling rig. Photo courtesy of Forespar

He adds that while he understands some sailors are wary of going with in-boom units because of their history of technical problems, these concerns are overblown. “If you can get the boom angle right and the main is cut right and the furler is installed correctly,” he says, “you’re going to be fine.”

Alan Massey, product manager for Forespar’s Leisure Furl line agrees, noting that once they’ve been configured correctly these kinds of systems provide a nice balance of performance and convenience. He adds that with an in-boom system like his, you can even reef or completely put away the sail on a reach or run, without having to round up into the wind.

“With in-boom furling you get ease of management. A lot of people today are able to sail big boats, and [in-boom furling] is the reason they can do so comfortably and safely,” Massey says.

Beyond that, he notes that although a mainsail must be sized to work with the furling system, building a mainsail for a boat with an in-boom furler isn’t that different from building a conventional main. Similarly, the state of in-boom furlers is such that sizing them for a catamaran isn’t particularly difficult either. Specifically, Massey says, because in-boom furlers are often used on very large monohulls, they are more than capable of handling the loads aboard a cat or tri. That said, when contemplating an in-boom system or specifying one for a new boat be aware there may be no room for a vang on a multihull design where the boom has been kept low to maximize the “P” (luff) length. Again, maintaining a correct boom angle is critical to the proper functioning of an in-boom furler and many setups include a solid vang for this reason. If there isn’t room for a vang, another option is a sturdy topping lift. Berman’s Balance 526, for example, carries two.

Another problem can be friction and chafe. Because batten cars can’t be incorporated into an in-boom system, the forward pressure of the battens, in particular, can create problem areas, making the sail more difficult to douse and set. It’s not necessarily a deal-breaker, but something to be aware of if you’re contemplating this kind of system.

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